Heterogeneous processes in chemistry and biotechnology are unit operations that encompass a solid member (including, but not limited to, immobilized chemical reagents, catalysts, scavengers, reaction supports, trapping sorbents, or immobilized biological materials such as enzymes, or cells or fragments thereof) contacting a fluidic medium carrying reactants or other agents, sample solutes, and/or products of the interactive processing of fluid-conveyed agent(s) with the solid member(s). Most such heterogeneous processes are critically dependent on convective flow of the fluidic medium to establish the necessary mass transfer between the fluidic and solid phases. As a consequence, solid/fluid heterogeneous systems are therefore often operated in a continuous flow through mode, in which case a conventional packed column with a suitable design is often the preferred format for encapsulating the solid member that is to be transited or percolated by the reaction medium. Numerous processes are, however, unfit for continuous processing. This applies in particular to processes where the solid member is a soft and compressible gel which is prone to collapse in a packed column bed, in transformation schemes where sequential addition of agents and/or removal of by-products or desired products are necessary, or where the physical or chemical conditions must otherwise be altered during the course of processing with the solid member. In those cases, a batch-wise processing model is often preferred. Such batch-wise heterogeneous processing can either be done by suspending the solid member directly in the fluid medium as particulate material under agitation, a process that will normally call for a filtration or sedimentation step to separate the phases after the process has been brought to an end. Alternatively, the fluidic medium can be circulated from the batch reactor through a packed reservoir containing the solid member by means of a specially designed flow system comprising pumps and/or valves or the like, in order to accomplish the convective mass transfer needed for the transformation to take place. Such reactors are often quite complicated and must regularly be built on-site and adapted for a specific purpose.
The challenge of establishing efficient convective mass transfer between solid and fluid phases has been addressed in different ways. Some interesting alternatives are disclosed in WO 2011/098570, which relates to devices for performing biological or chemical transformation, or physical or chemical trapping from, or release of agents to, a fluidic medium by means of a solid reaction member. These devices are comprised of a flow distributor having a fluid medium inlet, a fluid medium outlet, at least one confinement where said transformation, trapping, or release of agents is performed, and a means for rotating, rocking, wagging, or oscillating the flow distributor, by which action fluidic medium in which it is submerged is pumped through a bed of solid member contained within the flow distributor.
As a result of this pumping action, use of the devices disclosed in WO 2011/098570 leads to increased convective mass transfer, and accordingly improved performance of most heterogeneous transformation schemes. One of the reasons for these enhanced convective mass transfer properties is the ability of the flow distributor to use a combination of centrifugal force and flow dynamics to draw fluid through the central inlet(s) and discharge it through the peripheral outlets, resulting in a pumping action that predominantly draws fluid from the larger central inlet located at the bottom of the device. However, there is still a need for devices capable of providing even more increased convective mass transfer and an increased ratio between solid reagent and fluidic reaction medium, in order to improve the performance of biological and chemical transformation, physical and chemical trapping and release of agents by means of a solid reaction member even further. Factors that hamper the efficient use of flow distributor devices disclosed in WO 2011/098570 in a cylindrical reactor are the formation of solid body rotation and plughole vortices, accompanied by suction of gases, which can be difficult to get rid of, into the flow distributor. The conventional way of solving the problem of solid body rotation and vortex formation for standard impeller-stirred batch reactors (FIG. 1) is to disturb the rotational flow in the reactor by furnishing the vessel with a set of baffles 10 (H. A. Jakobsen, “Chemical reactor modeling: Multiphase reactive flows”, Springer Verlag: Berlin/Heidelberg, 2008; pp. 679-684), which are normally implemented as several (typically four) vertical flow-interrupting elements that are placed at some distance from the inner wall of the reactor in order to avoid the formation of unstirred fluid pockets. However, as is evident from FIG. 1, the inclusion of a conventional set of baffles results in a substantial increase in the total fluid volume of the reactor. Such excess volume is often detrimental to the kinetics of the intended transformations, since it will prevent the use of a high volume ratio between the solid reaction member and the fluidic phase. For an equal charged amount of reactants in the fluid phase, the concentration will thereby become lower, which has a negative effect on reaction kinetics in most cases. Conventional baffles are furthermore impractical to implement in small scale laboratory reactors.